FOUR-ELEMENT LENS Russian patent published in 2011 - IPC G02B9/34 G02B13/14 

FIELD: physics.

SUBSTANCE: proposed device comprises four separate lenses. First element is biconvex lens, second element is concave-plane lens with plane facing the image, third element is convex-plane with plane facing the image, or a positive meniscus with convex facing the object, and the fourth element is a negative meniscus with convex facing the object. Behind negative meniscus, there may be located one or several prisms and/or plane parallel plates. For radii of optical surfaces, index of refraction and coefficient of dispersion of lens material, thickness of negative meniscus and focal distance, relations are observed specified in claims.

EFFECT: higher polychromatic coefficient of modulation transmission.

3 cl, 2 dwg, 4 tbl